Glass fibers for the transmission of communications, drawn from so-called preforms, cannot be processed further in that condition. Just guiding the blank fiber over deflection pulleys makes it necessary to coat the fiber, to maintain its high starting strength. But protection prior to fiber bending (microbending) also makes it necessary to coat the individual fibers. For this purpose, one or more coatings, for example of a polymer material, are applied to the glass fiber jacket, where these show regular differences in their mechanical properties when applied in several layers. Thus, a relatively soft polymer coating can be applied to the blank fiber, as a so-called primary coating for protection prior to microbending, while a secondary coating with a material of increased E-modulus provides the external mechanical protection and increases the longitudinal rigidity of the fiber.
If a number of such protected fibers are placed in an optical cable, it is necessary to be able to identify the individual transmission elements, when such cables are installed. This purpose is served, for example, by a color coating applied to the outer cover, which surrounds it on all sides, but does not change the properties of the actual coating. However, such a color application surrounding the fiber is often not sufficient, to be able to keep the fibers of a cable reliably separate. For this reason, strands of the same color have already been provided with an annular marking, where the number of rings belonging together, or their distance, can be varied.
In this known marking process, the ring marking is performed in an additional work step, where solvent-containing identification colors are used, which must subsequently be subjected to a drying process. The adherence of the additional identification depends on the material used for the cover, or on the preparations that must be made before the marking process.